Vibrating tracer stylus



Jan. 23, 1951 L. E. MARCHANT VIBRATING TRACER STYLUS Filed Nov. 3, 1949HTTORNEY Patented Jan. 23, 1951 VIBRATING TRACER STYLUS Lawrence EdgarMarchant, Toronto, Ontario, Canada, assignor to A. V. Roe CanadaLimited, Malton, Ontario, Canada, a corporation Application November 3,1949, Serial No. 125,204

7 Claims.

This invention relates generally to tracing styli for duplicatingmachines, and more particularly to means for rapidly vibrating a stylusin order to reduce the effects of friction between the stylus and apattern over which it moves.

Generally speaking, in mechanical duplicating machines, a movable worktable mounted on a frame supports a pattern of the contour to bereproduced and a blank in which the contour is to be reproduced.Adjacent to the model is mounted a tracing stylus or follower, andadjacent to the blank is mounted a power-driven cutting head. The stylusand cutting head are fixed relatively to each other, or are arranged sothat the movement of the cutting head will be proportional to themovement of the stylus. Usually the work table is provided with drivingmeans that move the table in its own plane in two directions at rightangles to each other, the work table being usually reciprocated in onedirection and indexed or moved by small increments in the otherdirection.

It has been found that vibrations induced in a stylus enable it to movemore freely over the pattern contour, thus enabling the cutting head ato reproduce in the blank more faithful copies of the pattern contour.It has also been found that the vibrations induced in the stylus shouldpreferably be rapid but of comparatively small amplitude.

It is therefore an object of the invention to provide in a stylus avibrating device which produces rapid low-amplitude vibrations.

A further object of the invention is to prov de a stylus vibratingdevice which may conveniently be a plied to conventional du licatingmachines.

All of the foregoing and still f"rther objects and advantages of theinvention will become apparent from a study of the followingspecification. taken in conjunction with the accompanying drawings.wherein like characters of re erence indicate corresponding partsthroughout the several views and wherein:

Fig. 1 is a broken away perspective view of a tracer stylus embodyingthe invention; and

Fig. 2 is a perspective view of a tracer stylus embodying an alternativeform ofv the invention.

Referring to Fig. 1, an ordinary stylus holder 3 is provided with acollet type locking nut 4 which clamps the shank of a stylus 5, the freeend 5a of the stylus being adapted to beavagainst a pattern 6. Suitablysecured to the stylus immediately below the locking nut is a collar Ihaving an upper internal flange la and a lower internal flange lb whichdefine an annular chamber 8. An inlet pipe 9 which extends through thecollar into the chamber 8 is adapted to be connected by a length offlexible tubing ID to a supply of fluid under pressure, preferablycompressed air.

The internal periphery of the upper flange 1a of the collar makes asubstantially air-tight joint with the stylus 5 whereas there isprovided in the internal periphery of the lower flange lb of the collara helical groove 10 which is essentially a coarse thread. The crests ofthe thread engage the stylus, the thread grooves thus forming a helicalconduit connecting the chamber 8 to the space below the lower flange11).

Concentrically mounted below the collar 1 and spaced therefrom is acup-like member II which provides a race I2 in which a small steel ballI3 is free to roll in a circular path around the stylus 5. The diameterof the ball should be substantially greater than the space or gapbetween the collar I and the cup-like member I I.

In operation, high pressure air is admitted to the chamber 8 through theinlet pipe 9 and the flexible tubing It]. In order to escape from thechamber 8, the air travels downwardly through the helical conduitprovided by the groove 10, which imparts a rapid whirling motion to theair and discharges it into the race I! where it causes the steel ball I3to rotate rapidly around the stylus 5. The air is finally exhausted toatmosphere through the gap between the collar 1 and the cup-like memberI l.

The rotation of the ball [3 around the stylus 5 produces an unbalance inthe stylus of a frequency proportional to the speed of rotation of theball around the stylus and an amplitude proportional to the weight ofthe ball and to the diameter of the race. The vibrations thereby inducedin the stylus cause variations in the pressure of the stylus against thepattern 6, which variations in pressure tend to relieve the frictionaldrag of the stylus against the pattern, and prevent the stylus fromsticking and advancing with a jerky motion.

In an alternative embodiment of the invention illustrated in Fig. 2, asmall elementary turbine rotor hi is rotatably mounted on a stylus I5shown bearing against a pattern it, by means of a ball bearing memberI], the inner race of which is pressed onto the stylus. The turbinewheel is deliberately unbalanced by removing a small amount of metal atone point or by other means well known in the art. High pressure airfrom a nozzle l8 impinges tangentially against the turbine wheel; thiscauses the turbine wheel to rotate at a high speed, and because of theunbalance in the turbine wheel vibrations of a frequency proportional tothe speed of rotation of the wheel and of an amplitude proportional tothe static unbalance in the wheel are set up in the stylus !5, as in thepreferred embodiment of the invention.

With either embodiment of the invention, the frequency of the vibrationsmay be varied at will by providing a suitable throttle in the compressedair supply; in order to avoid resonant effects it is desirable to avoidvibrating the tracer stylus at any frequency which is a multiple of thefrequency at which the cutter teeth engage the blank. The amplitude ofthe vibrations may be varied by changing the radius of rotation of therotating unbalanced mass or by changing the magnitude of the unbalance.

It is thought that the construction and use of the invention will beapparent from the above description'of-the various parts and theirpurpose. It is to be understood that the form of the invention herewithshown and described is to be taken as: a preferred example of the sameand that various changes in the shape, size and arrangement of parts maybe resorted to, without departing from the spirit of the invention orthe scope of the subjoined claims.

What I claim as my invention is:

1. In atracer having a stylus adapted to bear against a pattern, meansfor vibrating the stylus comprising a mass rotatably mounted on thestylus and unbalanced about its centre of rotation, and means forrotating said mass.

2. In a tracer having a stylus adapted to bear against a pattern, meansfor vibrating the stylus comprising a mass rotatably mounted on thestylus and unbalanced about its centre of rotation, and means forrotating the mass including a nozzle arranged to direct a flow of fluidwhich impinges on the rotatable mass eccentrically of its centre ofrotation.

3. In a tracer having a stylus adapted to bear against a pattern, meansfor vibrating the stylus 4 comprising an endless race mounted on thestylus, a rollable body adapted to travel in the race, and means forcausing the rollable body to travel in the race, including a nozzlearranged to direct a flow of fluid on the rollable body.

4. In a tracer having a stylus adapted to bear against a pattern, meansfor vibrating the stylus comprising an annular race mounted on thestylus and having the stylus as its centre, a rollable body adapted totravel in the race, and means for causing the rollable body to travel inthe race, including a collar mounted on the stylus adjacent the race, aconduit in the collar having one end connected to a supply of fluidunder pressure and its other end being open and directed in the race toeject a flow of fluid which impinges on the rollable body.

5. In a tracer having a stylus adapted to bear against a pattern, meansfor vibrating the stylus comprising an annular race mounted on thestylus and having the stylus as its centre, a rollable body adapted totravel in the race, and means for causing the rollable body to travel inthe race, including a collar mounted on the stylus adjacent the race, achamber in the collar and connected to a supply of fluid under pressure,a helical conduit in the collar coiled around the stylus and having oneend connected to the chamber and its other end opening into the race fordirecting a flow of fluid into the race to roll the rollable .body inthe race around the stylus.

6. In atracer, having a stylus adapted to bear against a pattern, meansfor vibrating the stylus com-prisingan unbalanced wheel. mounted on thestylus and means for rotating the wheel about the stylus.

7. In a tracer having a stylus adapted to bear against a pattern, meansfor vibrating the stylus comprising a turbine wheel rotatably mounted onthe stylus which provides its axis of rotation, and a nozzle arranged todirect a flow of fluid. on the wheel to rotate it about the stylus. V

LAWRENCE EDGAR MARCHANT,

-No references cited.

